The present invention relates to an improved housing assembly for an underwater camera with a flash device, the housing assembly comprising a hollow cylindrical pressure housing which includes a shell having a window for the objective of the camera and which has a transparent pressure tight head for the flash device that includes a flash lamp.
Housing assemblies for underwater cameras having a built-in flash device are known, and in such known housing assemblies, the objective of the camera is arranged behind a first window in the shell of the cylindrical pressure housing. For the purpose of avoiding any reflections with the underwater cameras, an additional window is provided in the shell for the flash device and the flash lamp of the flash device is mounted behind this second window. For best possible utilization of the exposure angle of the objective of the camera, the second window for the flash lamp is arranged as close as possible to the first window for the objective. Since housing assemblies for underwater cameras, which are more particularly used at great depths, have to withstand considerable differences in pressure, it is necessary to take particular care in the production and sealing of the windows in the assemblies. The two windows, disposed in juxtaposition, considerably weaken the wall of the cylindrical pressure housing, and this, in turn, has to be compensated for by selecting relatively large wall thicknesses. As a result, the underwater camera housing assembly becomes relatively heavy and large. In addition, the pressure housing, in the form of a cylinder, only permits relatively small windows if the wall is not to be too greatly weakened and if it is desired to use the underwater camera at great depths. This in its turn, means that an illumination of quite a narrow angle is obtained so that a large number of exposures are necessary for photographically covering a large zone or area.
Accordingly, the object of the present invention is to provide an improved housing assembly for an underwater camera designed for being used at great depths, and in which the expense for the incorporation of a flash device with the camera is reduced and which, at the same time, permits a wide-angle illumination. This object is achieved, according to the present invention, by the utilization of a pressure housing having a pressure-tight head made of transparent material, such as for example, transparent acrylic glass, in which the flash lamp is arranged.
Resulting from the design of the improved housing assembly for an underwater camera, in accordance with the invention, it is possible to dispense with the costly installation of an additional window for the flash device. A comparable construction from the material of the pressure housing would mean a substantial lengthening of the housing and a corresponding increase in weight of the complete housing assembly for the underwater camera to obtain a comparable illumination of the subject. It is true that the flash lamp is at a greater spacing from the objective of the camera than with the known housing assemblies for underwater cameras, but the transparent head in which the flash lamp is arranged or disposed permits, in practice, illumination all round in the radial direction. Moreover in the axial direction vis-a-vis the housing assembly, in which the illumination is restricted in the direction of the pressure housing by the upper edge of the latter, a best possible adaptation to the existing exposure conditions is obtained by the fact that, allowing for the refraction of the light beams, the light source which is formed by the flash lamp is positioned at such a distance in the head that there is produced a covering of the exposure zone of the objective of the camera and of the divergent pencil of rays of the light source in the plane of the subject. Since the head, in practice, forms one closure means of the pressure housing, the dealing also does not raise any problems.
A best possible pressure tightness of the head is obtained by the fact that the head is a solid cylinder which comprises a bore open towards the interior of the hollow pressure housing and in which the flash lamp is seated. So as to keep as low as possible the technical and manufacturing costs, bearing in mind the optical possibilities, the bore of the head and the flash lamp, which is arranged in the latter, are disposed axially. Since the underwater camera normally only comprises one objective, it is possible to increase the intensity of the illumination of the subject by a reflector which is provided in the bore of the housing and which is pointed in the direction of the objective of the camera.
It is possible to produce a simple connection of the head with the pressure housing by the head having a threaded part, by which it is screwed onto the end of the pressure housing. For this purpose, the head is advantageously provided on the underside which has a central threaded connector and which is screwed into the end of the pressure housing and through which the bore passes.
According to another embodiment of the present invention, the head includes an annular flange which is drawn or extended downwardly and which is provided with an internal thread. The end of the pressure housing has an external thread, onto which the head is screwed by means of the flange. The possibility which arises in this case is that the bore, and hence the flash lamp, is provided near the wall of the pressure housing, as a result of which the illumination angle in the axial direction towards the objective is enlarged.
A reliable sealing at the abutment surfaces between head and pressure housing is obtained by an O-ring seal being arranged between the underside of the head and that annular surface of the end of the pressure housing which faces the head, the O-ring advantageously lying in an annular groove in the ring surface of the pressure housing.